Electric fuse



y 1934- c. D. THOMPSON 1,956,839

ELECTRIC FUSE Filed Aug. 5, 1931 Fig i. 12; 6.

T .E E

Envcwtoz Maw Patented May 1, 1934 UNITED STATES PATENT OFFICE ELECTRIC FUSE Application August 5, 1931, Serial No.

7 Claims.

The present invention relates to an electric fuse and aims to provide certain improvements therein.

An object of the present invention is to pro- 5 vide a means for obtaining a complete break in electrical circuits and one which is especially adapted to high voltage circuits where there may be a leakage of currents across short gaps. A further object of the invention is to provide a fuse or means for obtaining substantially simultaneous ignition of a number of ends of blasting safety fuse by means of electrical current.

Heretofore a metallic wire has been most gen erally used as a fuse or circuit breaker for currents of high voltage and low amperage, the effect of an overload on such'wire being to raise the temperature thereof to a point where a section of the wire fuses, thereby breaking the flow of current through the circuit. It has been 00 found, however, in such circuits, that the fused section of the wire is, as a rule, so short that in many instances leakage of current takes place through the broken section of the wire, thereby defeating the function of the fuse to completely break the circuit when overloaded.

According to the present invention I have found that by surrounding or coating the fuse wire with a highly combustible and preferably inflammable substance having a low kindling tempera- 30 ture, such, for example, as quick-match, black or smokeless powder and the like, that when the temperature of the wire is raised by the passage of electrical current therethrough to the kindling temperature of the combustible substance, ignition of said combustible substance will take place and the fuse wire will be broken over a length approximately the same as that occupied by the combustible substance and thus completely break the circuit.

A preferred embodiment of my improved electric fuse and the manner in which the same can be used to accomplish the objects of the invention are illustrated in the accompanying drawing, wherein Figure 1 is an elevation of a fuse embodying my invention, parts thereof being broken away to more clearly illustrate the structure thereof.

Fig, 2 is a transverse section taken substantially along the plane of the line 2-2 of Fig. 1.

Fig. 3 is a diagrammatic representation of the manner in which my improved electric fuse may be used for simultaneously igniting a plurality of ends of blasting safety fuse.

Fig. 4 is a section taken substantially along the plane of the line 4-4 of Fig. 3.

Figs. 5 and 6 are fractional views similar to Figs. and f showing a slightly modified manner of connecting the electric fuse to the blasting safety fuse.

Referring first to F gs. 1 and 2 of the drawing, let A indicate an electrical conductor in the form of a fine fusible wire he ends of which are bent back upon itself, as indicated at a, so as to reinforce the same and provide conic ct securing means a for the fuse. for substantially the length of the fuse and preferably disposed in longitudinal relation to and in contact with the wire are a plurality of strands B of quick-match, said wire and strands of quickinatch being bound together by means of countering yarns C spirally wound outside the quickmatch, and the resulting structure enclosed within a housing D which may be formed of any suitable material, which is preferably wateproof, such as cellophane or the like. It is also preferable that there be air spaces between the quickmatch and the wall of the housing so as to assist in supporting the combustion of quick-match and thereby insure a fusing of the wire over a length substantially equal to that of the quiclo match. In lieu of quick-match as the combustible material having a low kindling temperature, it will be appreciated :iat analogous results may be obtained with other substances having a low kindling temperature and a high heat value, and in some instances by coating the Wire with a selfcontained, highly combustible material, such as black or smokeless powder. The construction of the fuse is such that it is capable of manufacture in continuous length and can be cut to size to suit the particular use to which it is applied.

In Figs. 3 to 6 of the drawing, I have shown the manner in which a plurality of ends of blasting safety fuse can be substantially simultaneously ignited by the flame produced in passing an elec trical current through a length of electric fuse such as above described. To accomplish this the ends (2 of the separate lengths of blasting safety fuse E, which are attached to detonating caps or other explosive charges F, are attached to the 4 electric fuse G in any convenient manner, for example, by cutting a notch e in the safety fuse E, into which notch the electric fuse G may be held by an elastic band or string H, as shown in 4. An alternative method of connecting the electric fuse to the safety fuse is shown in Figs. 5 and 6, wherein the electric fuse G is passed or threaded through a hole e cut transversely through the blasting safety fuse E in proximity to its end 6. Upon completing an electric circuit through the Surrounding the wire A g u fuse G through the wires 5/, g, for example, by connecting the ends of said wires to a battery J or power line, the combustible material within the fuse G will ignite the ends e of the blasting fuses E, thus enabling an operator to practically simultaneously ignite a plurality of lengths of safety fuse to set off a plurality of explosive charges while remaining at asafe distance from the blast. It w"; be appreciated that by the foregoing method of simultaneously ,nitnig a plurality of lengths of safety fuse, the length of safety fuse so used can be considerably shortened and thus provide a substantial saving in the amount of blasting fuse used.

From the foregoing detailed description of the invention and the manner in which the same may be used, it v'll be appreciated that the objects of the invention as forth in the opening statement can be accomplished in a highly satisfactory and economical manner. t is to be understood, however, that while I have sh rm and described a single preferred emoodiment of my invention and but we specific applications thereof, I do not wish to be limited to the details of construction of the electric fuse describ d nor to the manner of its use with blastii ety fuse, since it will be apparent to any one mll d in the art that said details of construction, well as its applications, may be varied without departing from the spirit the intention.

What I claim is:

1. El ctric fuse comprising a fusible conductor for carrying the entire normal current, a. combustible material in contact with the conductor adapted to be ignited thereby and destroy the conductor to completely break the current flow through the fuse upon the temperature of the conductor being raised to its fusing point by an excess of current, and a closure member for said conductor and combustible material providing air spaces between the combustible material and the closure member.

2. Electric fuse comprising a fusible conductor for carrying the entire normal current, a coinbustible material in contact with the conductor adapted to be ignited thereby and destroy the conductor to completely break the current flow through the fuse upon the temperature of the conductor being raised to its fusing point by an excess of current, and a waterproof envelope within which said conductor and combustible material are housed, providing air spaces between the combustible material and the envelope.

8. Electric fuse comprising a fusible conductor for carrying the entire normal line current and quick-match held in contact therewith.

4. Electric fuse comprising afusible wire for carrying the entire normal line current, strands of quick-match extending longitudinally of the wire and means for holding said quick-match in contact with said wire.

5. Electric fuse comprising a fusible wire for carrying the entire normal line current, strands of quick-"hatch surroruiding the wire, means for holding said quick-match in contact with said wire, and a closure member for said elements providing air spaces between the quick-match and the closure member.

6. Electric fuse formable in a continuous length and adapted to be cut up into various lengths in accordance with varying needs, consisting of a fusible conductor for carrying th entire normal line current, a combustible material having a low kindling point and a high heat value held in contact with said conductor and adapted to be ignited thereby upon the temperature of the conductor being raised to its fusing point by an excess of current, and a closure member surrounding said wire and combustible material.

7. Electric fuse formable in a continuous length and adapted to be out up into various lengths in accordance with varying needs, consisting of a fusible conductor for carrying the entire normal lin current, strands of combustible material having a low kindling point and a high heat value in contact with said conductor and adapted to be ignited thereby upon the temperature of the conductor being raised to its fusing point by an excess of current, means for holding said combustible material in contact with said conductor, and a closure member surrounding said elements.

CHESTER D. THOMPSON. 

